Autophagy plays a positive role in zinc-induced apoptosis in intestinal porcine epithelial cells

A high-zinc (Zn) diet has been found to promote growth performance in pigs, but causes cell apoptosis in the intestinal epithelium. To investigate the mechanism underlying the high dietary Zn-induced apoptosis in porcine small intestinal epithelium, IPEC-J2 cells (intestinal porcine epithelial cells) were used to determine the effect of Zn on cell inhibitory, apoptosis, and mitochondrial membrane potential and autophagy in vitro. Results showed that Zn inhibited IPEC-J2 cell proliferation and induced apoptosis and autophagy. High concentrations of Zn induced DNA fragmentation and nuclear morphological changes, and increased intracellular Zn concentration. It also increased the protein expression level of cleaved caspase-3, caspase-8, beclin 1 and microtubule-associated protein 1 light chain 3 (LC3)-II, and the translocation of cytochrome c (Cyto C) into cytosol from mitochondria, and decreased the protein expression level of P62/SQSTM1. While 3-MA (3-methyladenine, as an autophagy inhibitor) suppressed the Zn-induced changes in the protein expression level of cleaved caspase-3 (CASP3), caspase-8 (CASP8), Cyto C, beclin 1, LC3-II and P62/SQSTM1. 3-MA decreased the Zn-induced mitochondrial apoptosis. High concentration of Zn up-regulated the relative mRNA expression level of BAX, CYCS, CASP3, CASP8, LC3-II and P62/SQSTM1 genes (p < 0.05), which were also ameliorated by 3-MA supplementation. In conclusion, autophagy inhibition significantly reduced the Zn-induced loss of mitochondrial membrane potential and attenuated the elevation of apoptosis in IPEC-J2. Autophagy and apoptosis act as partners in the Zn-induced cellular death in IPEC-J2.